1. Field of the Invention
The present invention relates to a gas laser apparatus which discharges and excites laser medium gas to oscillate (output) laser light.
2. Description of Related Art
There has been known a gas laser apparatus which is provided with a pair of main discharge electrodes and preionization electrodes, and discharges to excite laser medium gas (hereinafter, simply referred to as gas) to oscillate laser light (for example, excimer laser light). Such the apparatus has a configuration shown in FIG. 1, in which a spark discharge is made between each of the pairs of preionization electrodes 2a and 2b disposed opposite to each other thereby to discharge and excite the gas sealingly filled in a chamber 1. Then, the ultraviolet light and electrons which are generated by the discharge and excitation are supplied to between main discharge electrodes 3a and 3b, causing a glow discharge with optical resonance, thereby oscillating laser light.
The chamber 1 of an almost perfect circular form in section is provided therein with a fan 4 used for gas circulation. A gas flow generated by the fan 4 prevents the gas which has been deteriorated by the discharge from stagnating between the electrodes 2a, 2b, 3a, and 3b. This fan 4 is arranged in an appropriate position for conveying (sending) the gas to the electrodes, without interference with a dust collector, a cooling pipe, and other components provided within the chamber 1, which are not shown in FIG. 1.
Provided inside the chamber 1 is a guide plate 5 for efficiently producing a flow of the gas from the fan 4 to the electrodes. The mounting position and shape of this guide plate 5 are determined by fluid mechanical calculations, verification experiments, and others. Furthermore, a restriction plate 6 is disposed for allowing the gas to efficiently flow to the electrodes. This restriction plate 6 is arranged to configure a gas passage B toward the electrodes in cooperation with the guide plate 5.
As the number of parts or members increases, however, the structure of the apparatus becomes more complex with an increased cost.
Meanwhile, in an apparatus which oscillates excimer laser light by using fluorine gas, an increase in contact areas of the apparatus with the gas would cause fluorine absorption to the surface of parts. This reduces gas purity, but increases impure gas which will decrease oscillation efficiency.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a gas laser apparatus capable of efficiently, stably oscillating laser light without needing complex structure.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a gas laser apparatus including: a chamber in which laser medium gas is sealingly filled; a pair of main discharge electrodes arranged opposite to each other in the chamber; and a fan disposed in the chamber; wherein the chamber has an inner wall of a substantially elliptic shape in a plane perpendicular to a lengthwise direction of the chamber, and a part of the inner wall being between the fan and the main discharge electrodes serves as a guide for guiding the gas made to flow by the fan toward the main discharge electrodes.
According to another aspect of the present invention, there is provided a gas laser apparatus including: a chamber in which laser medium gas is sealingly filled; a pair of main discharge electrodes arranged opposite to each other in the chamber; a fan disposed close to an inner wall of the chamber; a first restriction plate disposed between the fan and the main discharge electrodes, which restricts a flow of the gas from the fan; a second restriction plate arranged in almost symmetric relation to the first restriction plate about a center line of the chamber, which restricts a flow of the gas from the main discharge electrodes; wherein the chamber has an inner wall of a substantially elliptic shape in a plane perpendicular to a lengthwise direction of the chamber, and a part of the inner wall being between the fan and the main discharge electrodes serves as a guide for guiding the gas made to flow by the fan toward the main discharge electrodes.
Furthermore, according to another aspect of the present invention, there is provided a gas laser apparatus including: a chamber in which laser medium gas is sealingly filled; a pair of main discharge electrodes arranged opposite to each other in the chamber; a fan disposed in the chamber; wherein a part of the inner wall being between the fan and the main discharge electrodes serves as a guide for guiding the gas made to flow by the fan toward the main discharge electrodes.